“Commonly known as the stomach flu, norovirus has been around forever, and has become the leading cause of gastroenteritis or inflammation of the intestinal tract that causes vomiting and diarrhea,” says Dr. Edmund Milder, a pediatric infectious disease specialist at Rady Children’s Hospital and UC San Diego Health.

Norovirus outbreaks have been surging in several provinces and the U.S. as winter weather forces people indoors. The highly contagious gastrointestinal virus is easily spread in crowded settings such as schools,

A surge in norovirus cases might be explained by a new strain of the virus, which now reportedly makes up a majority of outbreaks across the U.S. This winter’s dominant norovirus strain is a newer variant called the G11.

Norovirus is surging across the U.S., with case numbers higher now than they've been at the same time in more than a decade, according to the U.S. Centers for Disease Control and Prevention (CDC). There is no antiviral treatment for the miserable but thankfully short-lived illness,

In recent months, the U.S. and the Bay Area have seen a significant increase in norovirus cases, marking the highest outbreak levels in over a decade.